Abstract: The present invention relates to a composition for use in inhibition of crystallization and/or biofilm formation on an indwelling urinary catheter. The composition of the present invention comprises magnesium ions, potassium ions and citrate ions. Preferably the composition of the present invention consists of 74.2 weight % of tripotassium citrate monohydrate and of 25.8 weight % of anhydrous trimagnesium citrate. Its administration reduces the risk of obstruction of a urinary catheter, reduces the risk of a catheter-associated urinary tract infection, reduces the risk of bladder stone formation, reduces the risk of an injury of urethra mucosa as a result of exchange of the indwelling urinary catheter, and allows application of an indwelling urinary catheter for a prolonged period of time.